bad performance on madmax?

everyone go on about how well optimized this game is but i get really bad performance i don't know why i have a I5-2500k 3.3ghz 8 gig of ram. and a GTX 960 and i keep getting framedrop from 60 to 45 sudden drop and even lower sometime it doesn't seem to be linked to place in the game. can anyone help me?

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